The invention relates to plant propagation systems, and more particularly to aseptic propagation systems and methods.
Tissue culture propagation, sometimes referred to as micro propagation, is the process of growing plants from a piece of plant tissue that has been extracted from a parent plant. Horticulturists favor plant propagation as a growing method because its provides relatively high production efficiency and greater uniformity of plants. The process results in mass production of plants having certain desirable characteristics because substantially all the plants produced are genetically identical to and have all the desirable traits of the parent plant.
Plant micropropagation may be described as subdivided into stages. Stage one is sometimes said to comprise initiation, in which a plant bud is initiated in a growing media. Stage two comprises a multiplication phase in which nutrients and hormones are provided to enable rapid cell division and substantial growth of the platelets. In stage two, it is very important to keep pathogens and biological pests from infesting the culture. It is important to avoid subjecting the entire crop or field to biological pests, and one way to avoid subjecting the entire crop or field to biological pests is to propagate the plants in an environment that shields the maturing plant from pathogens, while also facilitating rapid and vigorous growth.
In stage three, leaves and shoots expand and the plant tissue becomes more capable of photosynthesizing. In stage four, the plant is moved out of the laboratory environment and into a greenhouse, where the plant may begin to take on larger amounts of light, and therefore heat, developing roots that will be needed for transfer to the field in the natural environment outdoors.
Environments conducive to root and shoot formation of the developing plant facilitates rampant spread of pests. Therefore, it is important to minimize the chances of introducing pests on plant material or media.
Apparatus and methods have been devised to micropropagate plants in the above referenced manner. For example, U.S. Pat. Nos. 5,525,505 and 5,597,731 are directed to plant propagation systems. These two referenced patents disclose sealed, semipermeable membrane vessels for completely enclosing plant material therein. The sealed vessels typically are translucent and permeable to gases and liquids while remaining impermeable to biological contaminates. Plant tissue extracted from a parent plant may be placed within the sealed vessels and grown heterotrophically. Once it develops, the plant may be transferred to a greenhouse environment for photoautotrophic growth. In the greenhouse environment, the sealed vessels are supported in trays, and exposed to light, gases, water, and a liquid nutrient solution for optimizing growth.
At least one patent has disclosed the use of a sealed sterile container with support members provided for plant tissues which are positioned between surfaces of the support members. U.S. Pat. No. 5,943,821 discloses support members within a sealed sterile container having opposing surfaces for supporting plant tissues made of a material that is suitable for impregnation by a nutritive medium. In the ""821 patent, a cylindrical container that resembles a Petri dish is disclosed. In fact, a Petri dish is the suggested container to be used in the practice of the invention disclosed in the ""821 patent, whereby such a hard cylindrical container may be sealed by means of plastic film, wax, or other material.
However, there are disadvantages with the use of such hard plastic containers. Such containers are relatively heavy, and therefore typically are very costly to ship from the laboratory to a greenhouse. Further, the containers must be re-used many times to make the use of such containers economically viable. Re-use requires that the containers be washed or sterilized, and then sent back to the laboratory. Storage also presents a problem, as the containers are not compressible (and sometimes not even stackable) which requires a large volume of space for storage. This storage problem adds to the undesirability of using such hard plastic tray containers as plant propagation containers.
What is needed in the plant propagation industry is a method and apparatus for producing plants in a manner that facilitates the entry of gases such as carbon dioxide into the vicinity of the plant. An apparatus that provides for light transmission and a steady nutrient supply is desired. Furthermore, a lightweight and inexpensive method of propagating large numbers of plants easily, reproducibly, reliably, and at a minimum cost to a grower is needed. Adequate nutrients and gases must be provided to the plant while at the same time shielding plant seedlings from undesirable biological pathogens. Furthermore, the apparatus must be capable of maintaining the plant at an appropriate temperature while the plant is propagating.
The present invention recognizes and addresses the foregoing disadvantages, and others of prior art constructions, and methods.
Accordingly, it is an object of the present invention to provide a plant propagation system.
It is another object of the present invention to provide a new method for propagating plant material.
It is a further object of the present invention to provide a plant propagation system and method that does not rely upon hard rigid containers.
It is another object of the present invention to provide a plant propagation system and method that prevents contamination of the growing plant material.
It is another object of the present invention to provide a plant propagation system and method that continually replenishes the nutrients and gasses necessary for plant growth.
It is further object of the present invention to provide a plant propagation system and method that facilitates the transportation of plant material.
It is a further object of the present invention to employ an apparatus for cooling plant containers during growth.
It is another object of the invention to replenish or change the composition of nutrients and gases necessary for plant growth. It is an objective to provide a system that is well suited to grow plants in several physiological stages and production environments.
The invention comprises plant propagation apparatus having a disposable sealed transparent enclosure having at least two walls. The walls, in one embodiment, are formed of a flexible material that facilitates transmission of light through the walls, the enclosure having an inner space and an outer surface. The enclosure is capable of sealing plant material in a substantially airtight manner. The enclosure is capable of maintaining on its inner space a reservoir of liquid nutrient solution for uptake by said plant material. The enclosure is configured to receive gas on its inner space to a predetermined level or pressure, thereby affording to the enclosure a flexible mechanical resistance. The enclosure is capable of protecting the plant material from mechanical stress during handling and transport while affording a flexible packing mechanism for the plant material.
In one embodiment, the apparatus also includes a gas diffusion membrane vent to facilitate diffusion of gases from the outer surface of the enclosure to the inner space of the enclosure. For example, air, oxygen, or carbon dioxide can enter the enclosure through such a membrane vent.
In other embodiments, the apparatus is adapted to assume a configuration that at least partially blocks the flow of gas across the gas diffusion membrane vent. This may be accomplished by folding over a membrane vent of the enclosure, or by blocking the membrane vent using a patch or cover. Furthermore, the membrane vent may be adapted to retard the communication of pathogens from the outer surface of the enclosure to the inner space of the enclosure.
In general, the enclosures are adapted to be placed side by side in a shipping carton for transport, the enclosure having a gas pressure on its inner space that facilitates close packing without substantial damage to the plant material. Large numbers of plants can be shipped easily in this way.
The invention also includes a system for propagating plants that comprises a disposable sealed transparent enclosure having at least two walls, the walls being formed of a flexible material that facilitates transmission of light through the walls. In this system, the enclosure has an inner space and an outer surface, the enclosure being capable of sealing plant material in a substantially airtight manner, whereby the enclosure is capable of maintaining on its inner space a reservoir of liquid nutrient solution for uptake by the plant material. The enclosure is also configured to receive gas on its inner space to generate pressure to a predetermined level. In this way, it is possible to afford to the enclosure a flexible mechanical resistance.
A support tray is also provided, the tray being adapted to thermally buffer the enclosure by supporting a cooling fluid, such as water, upon at least a portion of the outer surface of the enclosure.
The invention may also comprise a method of propagating plant material. In the method, several steps may be performed, at least some of which include: providing a flexible film, living plant material, and a nutrient solution, then sealing the flexible film to form an airtight three-dimensional enclosure having an inner space. In the method, the enclosure has on its inner space living plant material and a nutrient solution. Also, gas is provided to the inner space of the enclosure in an amount that affords mechanical stability to the enclosure. The enclosure is adapted to assume a volume and shape that is supportive of vertical growth of the living plant material. The enclosure is adapted to facilitate shipping and transport of the enclosure in packed boxes or crates.
In some methods, gas is injected through a hole in the wall of the enclosure, then the hole is resealed to provide an airtight enclosure. The method, in some embodiments, may also comprise removing the acclimatized plant material from the enclosure and then planting the living plant material in soil.